Recently, new robotic fields including coexistent robots and entertainment robots are under study and development in place of the industrial robot devices. Such robots are designed to implement an action on the basis of information such as external stimuli from sensors or the like.
For example, a method of creating a robot action on the basis of an evaluation done from the viewpoint of robot's self-preservation is disclosed in “Tetsuya Ogata and Shigeki Kanno: Creation of Robot Action On the Basis of Self-preservation—Methodology and Implementation of Machine Model, Journal of the Japan Academy of Robotics (1997), Vol. 15, No. 5, pp. 710-721 (will be referred to as “conventional art” hereunder). The “evaluation from the viewpoint of robot's self-preservation” is to evaluate a robot device from the viewpoints of durability and failure rate of the robot hardware. More specifically, a self-preservation evaluation function is calculated which is to convert environment information (inputs from visual and auditory sensors) as well as input information including state of the battery, power consumption, circuit temperature, etc. into an evaluation value (failure rate) of the robot device's durability from the standpoints of the hardware durability and failure rate, and the values of internal and external sensory information and self-preservation function are monitored to shift an action, being done, of a plurality of behaviors with a command for another action being actually given to the robot device. Thus, the robot device will reflect such acceptability that it will implement an action for a better evaluation of the self-preservation, not any action for a worse evaluation.
Also, the robot device can have introduced therein a self-preservation evaluation function for modeling “Sentiment”. It can express an emotion by appearing in yellow to show a joy when it is charged and in blue to show a fear when it is discharged, for example.
The evaluation, based on the “Self-preservation”, of the robot device disclosed in the conventional art is so simple that the “Charging” is evaluated to be good while “Discharging” is evaluated to be not good. That is, the evaluation can only lead to a one-way communication with the human being.
Many of the coexistent and entertainment robots, generally taken as toys, are designed to act only in response to external stimuli. That is, the relation between a user's operation and robot's response is a fixed one. Accordingly, the robot users get tired of such toy robots which repeat only the same action in response to the same external stimulus.
There have recently been proposed robot systems in which the emotions such as instinct and sentiment are modeled to manage the internal state of the system and an action is selected correspondingly to a variation of the internal state. In many of such robot systems, however, actions selectable in response to an internal state and external stimulus are fixed ones and it is difficult to select any action other than such fixed actions via an interaction between the user and environment.
If a function to have a robot implement a next optimum action or motion suitable for the current situation and a function to have the robot change a next action or motion on the basis of its past experiences can be installed in the robot, the robot will be able to have the user feel an increased affinity or satisfaction with the robot. This robot will give a larger amusement to the user, and its interaction with the user will be smoother.